Schism (multiple popes), simony (buying church jobs) & indulgences (selling forgiveness) caused reformers to speak out.
The Scala Sancta were supposedly the same stairs that Jesus ascended before Pilate. The priests claimed that if someone climbs each step on their knees, god forgives them for their sins. Martin Luther did this. He climbed each step seeking peace with god.
Diet of Worms
Martin Luther wrote the 95 theses, which were against the practice of selling indulgences by the Catholic church. They were posted on the door of the castle church
The Five Solas were written by the protestant reformers. They were basically 5 statements that summed up protestant belief. Martin Luther was considered a leader of the protestants.